Bump dill from 0.3.6 to 0.3.8 in /src/python

Bumps [dill](https://github.com/uqfoundation/dill) from 0.3.6 to 0.3.8.
- [Release notes](https://github.com/uqfoundation/dill/releases)
- [Commits](uqfoundation/dill@dill-0.3.6...0.3.8)

---
updated-dependencies:
- dependency-name: dill
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

src/python/requirements.txt

@@ -18,7 +18,7 @@ click==8.1.3
     # via
     #   -r src/requirements.txt
     #   black
-dill==0.3.6
+dill==0.3.8
     # via
     #   -r src/requirements.txt
     #   pylint